[Prev][Next][Index][Thread]
(meteorobs) Excerpts from "CCNet 55/2001 - 10 April 2001"
------- Forwarded Message
From: Peiser Benny <B.J.Peiser@livjm.ac.uk>
To: cambridge-conference <cambridge-conference@livjm.ac.uk>
Subject: CCNet, 10 April 2001
Date: Tue, 10 Apr 2001 11:06:36 +0100
CCNet 55/2001 - 10 April 2001
----------------------------
[...]
(3) A COMETS ODD ORBIT HINTS AT HIDDEN PLANET
Science News Online, 7 April 2001
(4) THOMAS GOLD REVIVES OLD DEBATE ABOUT MOON TO EXPLAIN DUST IN EROS
CRATERS
Ron Baalke <baalke@jpl.nasa.gov>
(5) HITCHHIKING MOLECULES COULD HAVE SURVIDED FIERY COLLISIONS WITH
EARTH
Andrew Yee <ayee@nova.astro.utoronto.ca>
[...]
======================================================================
(3) A COMETS ODD ORBIT HINTS AT HIDDEN PLANET
Science News Online, 7 April 2001
>From http://c.moreover.com/click/here.pl?e17359563&e=6513
Ron Cowen
Far beyond the solar system's nine known planets, a body as massive as
Mars may once have been part of our planetary system-and it might still
be there.
Although the proposed planet would lie too far away to be seen from
Earth, its gravitational tug could account for the oddball orbit of a
large comet spotted in the outer solar system a year ago.
Known as 2000 CR105, the comet moves about the sun in a much more
elongated pathway than originally thought, astronomers now find.
Observations over the past year by Brett Gladman of the Observatoire de
la Ctte d'Azur in Nice, France, and his colleagues show that the comet's
orbit takes it further than 200 astronomical units (AU) from the sun and
as close as 44 AU. One AU equals the Earth-sun distance of about 150
million kilometers.
Such an oblong orbit is usually a sign that an object has come under the
gravitational influence of a massive body. But 2000 CR105, which may be
an escapee from the distant reservoir of comets known as the Kuiper
belt, never gets anywhere near any of the solar system's familiar team
of nine planets. Even at its closest approach to the sun, the
approximately 400-km-wide ball of ice comes no closer than 14 AU to
Neptune, the nearest known candidate for a significant gravitational
interaction.
The astronomers concede that feeble and random pushes from Neptune could
have slowly nudged 2000 CR105 into its current orbit. However,
preliminary analysis suggests this scenario isn't likely, note Gladman,
Matthew Holman of the Harvard-Smithsonian Center for Astrophysics in
Cambridge, Mass., and their collaborators.
In an article the researchers recently posted on the Internet
(http://arXiv.org/abs/astro-ph/0103435), they suggest that a massive
body lurking among the tiny, frozen residents of the Kuiper belt could
have been the culprit.
That object could have been Neptune itself. According to one theory,
Neptune and Uranus first formed between the orbits of Jupiter and Saturn
and were then flung out to greater distances from the sun.
If that kick propelled Neptune into the Kuiper belt before the planet
settled into its current nearly circular orbit, its gravity could have
caused the orbits of several objects like 2000 CR105 to stretch into
elongated trajectories.
Alternatively, the comet's orbit could be the handiwork of an
as-yet-unseen planet whose mass lies somewhere between that of Earth's
moon and Mars, the researchers say. It's likely that such an object
would have coalesced in the outer solar system from the same debris that
formed Neptune, Uranus, and the cores of Jupiter and Saturn, Holman
notes.
There's only a 1 percent chance that a planet could have survived in the
Kuiper belt or its surroundings over the 4.5-billion-year age of the
solar system, says Holman. If the planet found a secluded nook of the
belt, however, it could remain intact today.
If the proposed planet is as massive as Mars, it would have to lie some
200 AU from the sun-about 7 times Neptune's distance-Holman calculates.
Were it closer, observers would have spotted it.
A planet lurking in the Kuiper belt now or in the past might also
explain why many members of the belt have orbits that angle away from
the plane in which the nine known planets orbit the sun.
"Undoubtedly, something [massive] knocked the hell out of the belt,"
says Harold F. Levison of the Southwest Research Institute in Boulder,
Colo. "The question is whether it's there now."
The stability of the orbit of 2000 CR105 suggests that any planet that
influenced the comet's path has long since departed. If astronomers find
a family of objects similar to 2000 CR105, the nature of their orbits
could indicate whether the hidden planet is in fact still there, Levison
says.
>From Science News, Vol. 159, No. 14, Apr. 7, 2001, p. 213.
======================================================================
(4) THOMAS GOLD REVIVES OLD DEBATE ABOUT MOON TO EXPLAIN DUST IN EROS
CRATERS
>From Ron Baalke <baalke@jpl.nasa.gov>
http://www.news.cornell.edu/releases/April01/Gold.dust.deb.html
Cornell cosmologist Thomas Gold revives old debate about moon to explain
movement of dust into craters of asteroid Eros
FOR RELEASE: April 4, 2001
Contact: David Brand
Office: 607-255-3651
E-mail: deb27@cornell.edu
ITHACA, N.Y. -- More than just dust was kicked up when NASA's Near Earth
Asteroid Rendezvous spacecraft, NEAR Shoemaker, made a successful
landing
on asteroid 433 Eros on Feb. 12. Also disturbed were the memories of an
experiment carried out more than three decades ago by a student of
Thomas
Gold, professor emeritus of astronomy at Cornell University.
Images of small craters on 22-mile-long Eros, sent back to Earth by the
NEAR spacecraft's camera, revealed a fine-grain material that has
somehow
found its way to the bottom of the craters. The members of the NEAR
imaging team, including the team's leader, Cornell astronomer Joseph
Veverka, expressed puzzlement over the movement of the dust that had
created flat, smooth floors in craters. There is, they said, some
unknown
mechanism that moves the dust around so that it slides down the craters'
sides, "ponding" in the bottoms.
Gold was, perhaps, the only observer not surprised. Static electricity,
he
argues, causes dust grains to levitate downhill into the bottom of
craters
- -- the same process, he believes, that has filled craters on the moon.
"If
you added a layer 1 micron [0.001 millimeters] thick in the time since
the
Pyramids were built [about 5,000 years ago], you could get a layer 1
kilometer in depth over a billion years," says Gold, who has long been
known as one of the world's foremost cosmologists.
"The features on Eros are so similar to those on the moon, that dust
levitation has now to be reconsidered for all large lunar features, and
major conclusions of lunar research now have to be reconsidered," says
Gold.
Electric charges on the grains, he says, were created by
charged-particle
bombardment from the sun's solar wind, a current of ionized atoms and
particles such as electrons and protons that the sun spews from its
surface. When electrons with a high enough energy hit the dust grains,
they either cause the grains to gain more negative charge or more
positive
charge, depending on the substance. "It's a very intriguing
possibility
and one which we will be evaluating seriously during the coming months,"
says Veverka, who is chair of Cornell's astronomy department.
Gold's controversial theory dates back to stormy debates that continued
through the 1950s into the early 1970s on the geology of the moon's
impact
craters and their flat, dust-filled floors. Gold himself had written his
first paper on the subject in 1955. And in the late 1960s his graduate
student, the late Gregory J. Williams, carried out research at Cornell's
astronomy department, which Gold chaired from 1959 to 1968, into the
electrostatic agitation of the surface layers of fine rock powders. In
1976, Williams' Ph.D. dissertation, Electrodynamics and the Moon --
Transport Mechanisms, expounded many of Gold's theories on the
transportation of dust on the moon.
The laboratory experiments found that dust particles under lunar
conditions
move when different grains adopt very different charges. The electrical
interaction sets up strong electric fields on a very small scale,
allowing
electrical forces to levitate and move the dust particles.
"Based on the details of reflection of sunlight, grains on the surface
had
to be small enough so they could pile on top of each other in a very
loose
formation, which my colleagues called 'fairy castle structures.' I can't
understand any process that could occur on the moon that would lift up
material the size of a brick, but I can understand processes that would
lift up 50-micron-sized grains," says Gold.
This contradicted the view of many geologists, who believed that lunar
craters typically were filled either by material ejected by meteoroid
and
asteroid impacts or by lava. However, says Gold, the smoothing and
filling
in of craters on the moon and asteroid Eros was not accomplished by
falling
debris from an impact (which would give a "snowed over" appearance to
the
land and rocks) -- and lava flows on tiny Eros are not possible.
"The amount of material that is missing from the craters on the side of
the
moon visible from Earth, if distributed all over that area, would make a
layer between one and two kilometers deep. You either have to say that
this material vanished from the moon, which is not likely, or that it
had
migrated downhill just as it would have done on Earth for different
reasons," says Gold.
The filling in of craters from dust levitation on Eros appears to Gold
to
be similar in nature -- and to be taking place at about the same rate --
to
the erosion present on the hidden side of the moon, which does not
receive
as intense an electron bombardment from the solar wind as does the side
facing Earth. Since Eros lies 289 million miles from the sun, it is hit
by
fewer higher energy electrons than the facing side of the moon.
Related World Wide Web sites: The following sites provide
additional information on this news release. Some might not be part of
the
Cornell University community, and Cornell has no control over their
content
or availability.
o Near Earth Asteroid Rendezvous Mission:
<http://near.jhuapl.edu/>
======================================================================
(5) HITCHHIKING MOLECULES COULD HAVE SURVIDED FIERY COLLISIONS WITH
EARTH
>From Andrew Yee <ayee@nova.astro.utoronto.ca>
University of California-Berkeley
Contact:
Robert Sanders, 510-643-6998, rls@pa.urel.berkeley.edu
05 April 2001
Hitchhiking molecules could have survived fiery comet collisions with
Earth, UC Berkeley experiment shows
By Robert Sanders, Media Relations
Berkeley -- Simulating a high-velocity comet collision with Earth, a
team
of scientists has shown that organic molecules hitchhiking aboard a
comet
could have survived such an impact and seeded life on this planet.
The results give credence to the theory that the raw materials for life
came from space and were assembled on Earth into the ancestors of
proteins and DNA.
"Our results suggest that the notion of organic compounds coming from
outer space can't be ruled out because of the severity of the impact
event," said research geologist Jennifer G. Blank of the Department of
Earth and Planetary Science in the College of Letters & Science at the
University of California, Berkeley.
Blank and her colleagues Randy Winans and Mike Ahrens of the Chemistry
Division of Argonne National Laboratory, and engineer-mathematician
Gregory Miller of the Applied Numerical Algorithms Group of Lawrence
Berkeley National Laboratory, will report their preliminary findings
on April 5 at the national meeting of the American Chemical Society
in San Diego, Calif. The talk is part of an April 4-5 session on
extraterrestrial organic chemistry organized by Blank and colleague
Max P. Bernstein, a chemist in the Astrochemistry Laboratory at NASA
Ames Research Center in California.
Blank's team shot a soda-can sized bullet into a nickel-sized metal
target containing a teardrop of water mixed with amino acids, the
building blocks of proteins. More than seventy varieties of amino
acids have been found in meteorites -- many the suspected cores
of comets that smashed to earth -- and are presumed to exist in
interstellar dust clouds.
Not only did a good fraction of the amino acids survive the simulated
comet collision, but many polymerized into chains of two, three and
four amino acids, so-called peptides. Peptides with longer chains
are called polypeptides, while even longer ones are called proteins.
"The neat thing is that we got every possible combination of dipeptide,
many tripeptides and some tetrapeptides," said Blank, a geochemist.
"We saw variations in the ratios of peptides produced depending on the
conditions of temperature, pressure and duration of the impact. This
is the beginning of a new field of science."
Freezing the target to mimic an icy comet increased the survival rate
of amino acids, she added.
The ballistic test was designed to simulate the type of impact that
would have been frequent in Earth's early history, some four billion
years ago, when rocky, icy debris in our solar system accreted to form
the planets in what must have been spectacular collisions. Much of the
debris would have resembled comets -- dirty snowballs thought to be
mostly slushy water surrounding a rocky core -- slamming into Earth
at velocities greater than 16 miles per second (25 km/sec).
The severity of the laboratory impact was akin to an oblique collision
with the rocky surface of the Earth -- a comet coming in at an angle of
less than 25 degrees from the horizon, rather than head on perpendicular
to the Earth's surface.
"At very low angles, we think that some water ice from the comet would
remain intact as a liquid puddle concentrated with organic molecules,"
ideal for the development of life, Blank said. "This impact scenario
provides the three ingredients believed necessary for life: liquid
water, organic material and energy."
Benton C. Clark, chief scientist of Flight Systems at Lockheed Martin
Astronautics, proposed in 1988 that if comets are slowed sufficiently,
for example by drag from the Earth's atmosphere, some water and organic
compounds might survive the collision. They would collect in what he
called a "comet pond" of concentrated organic material where life
could develop.
Though comet hunter Eugene Shoemaker estimated that in Earth's early
history only a few percent of comets or asteroids arrived at low enough
angles, the bombardment would have been heavy enough to deliver a
significant amount of intact organic material and water, according to
Blank's estimates.
The best known theory of the origin of life on Earth is that it derived
from complex molecules such as amino acids and sugars produced early
in the planet's history by electrical discharges in an atmosphere
replete with gases such as methane, hydrogen, ammonia and water. The
famous Miller-Urey experiment in 1953, conducted by Stanley Miller
and Harold Urey of the University of Chicago, demonstrated that a
lightening-like discharge in a test tube filled with these molecules
could produce amino acids.
Other scientists, however, have proposed that the building blocks of
life arrived from space. Astronomers have detected many kinds of
organic molecules in space, floating in clouds of gas or bound up in
dust particles. They range from the simplest -- water, ammonia, methane,
hydrogen cyanide and alcohols, including ethyl alcohol -- to more
complex molecules, including chains of up to eight carbon atoms.
Interestingly, of the more than 70 amino acids found in meteorites,
only eight of them overlap with the group of 20 which occur commonly
as structural components of proteins found in humans and all other
life on Earth.
To test whether water and organic compounds could survive the high
pressures and high temperatures of a collision, Blank and her
colleagues worked for three years to design a steel capsule that
would not rupture when hit with a mile-per-second (1.6 kilometer-
per-second) bullet fired from an 80-mm bore cannon at the University
of Chicago and later at Los Alamos National Laboratory. The target she
and her team developed -- a two-centimeter diameter stainless steel
disk about a half-centimeter thick -- was able to withstand about
200,000 times atmospheric pressure without bursting.
They filled the small cavity with water saturated with five amino
acids: three from the list of 20 that comprise all proteins in humans
(phenylalanine, proline and lysine) and two varieties detected in the
Murchison meteorite (aminobutyric acid and nor-valine). That meteorite
plummeted to the ground in 1969 in Australia and is thought to be the
core of a comet.
The liquid contents were analyzed afterwards at Argonne using liquid
chromatography and mass spectroscopy to determine the species and
concentrations of molecules present.
The survival of a large fraction of the amino acids and their
polymerization during the collision make the idea of an
extraterrestrial origin of organic compounds a strong contender
against the Miller-Urey theory, Blank said.
"About one comet per year arriving in a low-angle impact would bring
in the equivalent of all the organics produced in a year in an
oxidizing atmosphere by the Miller-Urey electric discharge mechanism,"
Blank estimated. "An advantage is you get all of it together in a
puddle of water rather than diluted in the oceans."
The next hitchhikers she plans to subject to a shock test are bacterial
spores, which some have proposed arrived on Earth via comet to
jump-start evolution.
The work was sponsored by the National Science Foundation, NASA and the
Department of Energy.
###
NOTE: Jennifer Blank returns from San Diego on April 9, but can be
reached via email during that time at jenblank@seismo.berkeley.edu .
Her office phone is 510-643-0540.
--------------------------------------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet)
--------------------------------------------------------------------
The CCNet is a scholarly electronic network. To subscribe/unsubscribe,
please contact the moderator Benny J Peiser <b.j.peiser@livjm.ac.uk>.
Information circulated on this network is for scholarly and educational
use only. The attached information may not be copied or reproduced for
any other purposes without prior permission of the copyright holders.
The fully indexed archive of the CCNet, from February 1997 on, can be
found at: http://abob.libs.uga.edu/bobk/cccmenu.html
DISCLAIMER: The opinions, beliefs and viewpoints expressed in the
articles and texts and in other CCNet contributions do not necessarily
reflect the opinions, beliefs and viewpoints of the moderator of this
network.
------- End of Forwarded Message
To UNSUBSCRIBE from the 'meteorobs' email list, use the Web form at:
http://www.tiac.net/users/lewkaren/meteorobs/subscribe.html
Follow-Ups: